Support Material for PETG-CF

Bambu Lab X1 Series Bambu Lab X1-Carbon
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Bambu Lab Filament:

  • Support for PA/PET print bed temp spec is 80 - 110 °C and the default setting is 100°C in Bambu Studio.
  • PETG-CF bed temp is 65 - 75 °C with 70°C as the default in Bambu Studio.

I’m new to 3D printing so I’m starting with a low knowledge base.
My first wild assumption was that PETG is similar to PET, hence the support selection. However I see that PET-CF has a build plate temp of 80-100°C making it much more compatible with the support.

I get an error when trying to print telling me the bed temperature exceeds the filament’s vitrification temp. I presume that means the bed temp for the support material is in excess of the PETG-CF bed temp.

What does the community suggest?

  1. Lower the build plate temp to 70°C for both the PETG-FC and Support for PA/PET combo?
  2. Just print at the current 100°C and 70°C degree setting with the door open?
  3. Order some PET-CF (and wait to print)?
  4. Other?

Secondarily -
I have some narrow 0.8mm gaps with long overhangs to be supported. I think getting support material out of there may be difficult. Would you suggest using water soluble support material instead? Is there a suggested brand to use with PETG-CF or PET-CF? One more curve ball. Humidity is not an issue with the part. Should I switch to PAHT-CF?

Thank you.

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No! PET and PETG are very different! You can not use the support material for PETG!

As the slicer warns you, PETG will become soft at around 85°C, so the bed temp will cause your print to not work. Likewise with the support for PE/PET. It will not really stick well to the heatbed at lower temps.

BUT! the more serious problem is, that PETG could start to degrade while switching to the support filament, as the support filament has to be also printed at a significant higher nozzle temp! If that happens, you might become problems with partial clogs inside the nozzle.

What works well for PETG is, using PLA as a support material.They do not stick together too well, have similar melting points, etc. Just make sure that you select the right plate for both, for me, I had good luck with the engineering plate at 65°C, both materials sticked well too it.

Regarding your narrow overhangs:
I do not really understand what exactly you mean. Can you attach a picture?

Regarding PVA:
It is not supported with the AMS. I have heard some people getting it to work, some didnt. If you are new, I wouldnt try it. It is just too flexible and will most likely jam.

Regarding PAHT:
Only use it, if you need the technical properties. What are your requirements? You should always chose the material that fits your needs, especially with such an expensive technical filament. It is also much harder to print than PETG-CF.

Lastly, make sure that your filaments are dry. Especially if you are printing something more complicated. It really saves you a lot of potential problems. Do not assume, that a new spool is dry, it might be, it might not be. If you have nothing else, use the printer to dry the filament. It works, just a bit slow.

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@christian.woznik already provided many valuable details.
Additionally, there are many posts on the topic with a valuable user experience that you may benefit from. e.g. Support Filament --> PETG for PLA and PLA for PETG and more

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Thank you for all the insights!